URL.canParse

By  on  

Parsing of URLs on the client side has been a common practice for two decades. The early days included using illegible regular expressions but the JavaScript specification eventually evolved into a new URL method of parsing URLs. While URL is incredibly useful when a valid URL is provided, an invalid string will throw an error -- yikes! A new method, URL.canParse, will soon be available to validate URLs!

Providing a malformed URL to new URL will throw an error, so every use of new URL would need to be within a try/catch block:

// The correct, safest way
try {
  const url = new URL('https://davidwalsh.name/pornhub-interview');
} catch (e) {
  console.log("Bad URL provided!");
}

// Oops, these are problematic (mostly relative URLs)
new URL('/');
new URL('../');
new URL('/pornhub-interview');
new URL('?q=search+term');
new URL('davidwalsh.name');

// Also works
new URL('javascript:;');

As you can see, strings that would work properly with an <a> tag sometimes won't with new URL. With URL.canParse, you can avoid the try/catch mess to determine URL validity:

// Detect problematic URLs
URL.canParse('/'); // false
URL.canParse('/pornhub-interview'); // false
URL.canParse('davidwalsh.name'); //false

// Proper usage
if (URL.canParse('https://davidwalsh.name/pornhub-interview')) {
  const parsed = new URL('https://davidwalsh.name/pornhub-interview');
}

We've come a long way from cryptic regexes and burner <a> elements to this URL and URL.canParse APIs. URLs represent so much more than location these days, so having a reliable API has helped web developers so much!

Recent Features

  • By
    6 Things You Didn&#8217;t Know About Firefox OS

    Firefox OS is all over the tech news and for good reason:  Mozilla's finally given web developers the platform that they need to create apps the way they've been creating them for years -- with CSS, HTML, and JavaScript.  Firefox OS has been rapidly improving...

  • By
    CSS Filters

    CSS filter support recently landed within WebKit nightlies. CSS filters provide a method for modifying the rendering of a basic DOM element, image, or video. CSS filters allow for blurring, warping, and modifying the color intensity of elements. Let's have...

Incredible Demos

  • By
    CSS Columns

    One major gripe that we've always had about CSS is that creating layouts seems to be more difficult than it should be. We have, of course, adapted and mastered the techniques for creating layouts, but there's no shaking the feeling that there should be a...

  • By
    MooTools 1.3 Browser Object

    MooTools 1.3 was just released and one of the big additions is the Browser object.  The Browser object is very helpful in that not only do you get information about browser type and browser versions, you can gain information about the user's OS, browser plugins, and...

Discussion

  1. picker

    It doesn’t work in Typescript (with node v22 and @types/node v22) because:
    TS2339: Property ‘canParse’ does not exist on type ‘{ new (url: string | URL, base?: string | URL | undefined): URL; prototype: URL; createObjectURL(obj: Blob | MediaSource):
    string; revokeObjectURL(url: string): void; }’.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!